Workshop schedules now stay consistent after checkout expiry and catalog edits

Expired workshop checkout attempts now clear themselves automatically, so an
abandoned payment step no longer leaves a misleading pending order in the
venue's records. This cleanup does not create a charge or booking, and completed
payments keep using the existing fulfillment and refund safeguards.

Each Workshop Library item now keeps its own class type. Editing one workshop
can no longer overwrite another workshop's schedule name, and repaired workshop
sessions retain the venue's existing Bring a guest exclusions.

The final production preflight also confirmed that the expired order retains a
linked Stripe PaymentIntent. The exact repair preserves that identifier so a
late success continues through the existing refund-required path without
creating a booking.